William Horatio Bates, Better Eyesight Magazine — February 1921
“ It was not the physical strain of looking at a point that produced the pain, because there was no physical strain, the eye being incapable of looking at a point. It was the mental effort of trying to do what was impossible. As pain can be produced by the mind without any local cause, so it can be prevented or relieved by the mind, no matter how great the local irritation may be. In other words pain is a mental interpretation of certain stimuli, and under certain circumstances such stimuli are not interpreted as pain. ”
